Following the ITRS roadmap, transistor structures are becoming smaller and smaller. Today, nanoscale structures having suitable and stable properties, as for instance nanowire (NW) transistor channel structures (e.g. in gate-all-around (GAA) transistor structures), are desired. Producing such nanoscale structures is not evident.
It has been shown that forming a gate-all-around (GAA) or nanowire (NW) transistor structure by means of local oxidation of the lower surface of a fin structure leads to an irregular, unwanted shape of the channel. This results in lack of stability and controllability of the properties of the produced transistor structures.
In US 2011/0316080 a method is described for fabricating a fin transistor structure, comprising forming a fin on a substrate, wherein an insulation material is formed between a portion of the fin serving as the channel region of the transistor structure and the substrate.
There exists a need for improved and alternative methods for forming transistor structures comprising a nanowire channel structure.